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Author Topic: The Ross Ice Shelf Thread  (Read 1169 times)

Stephan

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The Ross Ice Shelf Thread
« on: February 17, 2019, 09:04:01 PM »
I just wondered that the largest Antarctic Ice Shelf - the Ross Ice Shelf - does not have its own thread. You can see it constantly growing, almost no cracks at its northern edge, apart from two or three seemingly elder ones. And so it didn't show larger calving events for many years or even decades.
Yesterday the northeasternmost corner of it showed a minor calving, an area of around 10 x 2 km broke off, in an area already full of cracks, see attached picture.
« Last Edit: February 17, 2019, 09:15:04 PM by Stephan »

oren

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Re: The Ross Ice Shelf Thread
« Reply #1 on: February 19, 2019, 12:51:07 PM »
ASLR had a combined RIS/FRIS thread.

Gray-Wolf

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Re: The Ross Ice Shelf Thread
« Reply #2 on: February 19, 2019, 01:31:43 PM »
Sorry Oren when I search on that all I get is your post above coming back?

My interest in the cryosphere was piqued with a huge crevice on Ross ( from roosevelt to mid shelf) to the point that I spoke with a few guys down at McMurdo who were ,that season, putting sensors along the length of it to monitor movement there?

https://worldview.earthdata.nasa.gov/?p=antarctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&t=2019-02-17-T00%3A00%3A00Z&z=3&v=-440576,-1281664,-90880,-1121664

I've watched it for over a decade now so the last couple of years of lower sea ice might be allowing more mechanical strains into the shelf hastening its eventual calve?

Through the noughties we saw warm basal water travelling down from the peninsula after it snuck under the circumpolar current (through valleys on the ocean bed) . this water arrived at Ross up to 5 years ago so impacting the grounding line of the shelf?

How close to the crack is this undercut now?
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Tor Bejnar

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Re: The Ross Ice Shelf Thread
« Reply #3 on: February 19, 2019, 04:21:09 PM »
I believe Oren was referring to the thread called
Hazard Analysis for the FRIS/RIS in the 2012 to 2060 Timeframe
I think using the 'search' tool only looks in the folder you are in. When searching for "RIS" in "Antarctica", it finds "FRIS/RIS", if in "The Ross Ice Shelf Thread", you only find Oren's post.

ASLR had a combined RIS/FRIS thread.
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gerontocrat

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Re: The Ross Ice Shelf Thread
« Reply #4 on: February 19, 2019, 04:49:15 PM »
I believe Oren was referring to the thread called
Hazard Analysis for the FRIS/RIS in the 2012 to 2060 Timeframe
I think using the 'search' tool only looks in the folder you are in. When searching for "RIS" in "Antarctica", it finds "FRIS/RIS", if in "The Ross Ice Shelf Thread", you only find Oren's post.

ASLR had a combined RIS/FRIS thread.
You can broaden or narrow your search
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FredBear

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Re: The Ross Ice Shelf Thread
« Reply #5 on: February 19, 2019, 04:59:40 PM »
The big Ross calving was Mar.14-17 2000, the Ross "coastline" in EODIS appears to be set in 2011 and the shelf has been growing outwards since then.
Most of the Ross ice shelf is not grounded, so can be melted by any available 'warm' water.
I attach an image from:-

Ice Sheet Stability and Sea-Level Rise

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« Last Edit: February 19, 2019, 05:06:37 PM by FredBear »

maga

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Re: The Ross Ice Shelf Thread
« Reply #6 on: February 19, 2019, 10:50:53 PM »
Just a comment to Stephans post above: My impression is that it is a piece of old fast ice that broke off, not a real ice berg. But note as well that the major crack directly below the date has expanded several kilometers to the west this year. However, I still expect the next major calving to occur along the even bigger crack behind within the next few years.

Stephan

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Re: The Ross Ice Shelf Thread
« Reply #7 on: February 21, 2019, 08:38:59 PM »
Looking at the shadow this iceberg produces om the water you may be right. It is probably much thinner than a "real ice berg" deriving from the shelf itself and therefore it is likely just a piece of older fast ice closely joint to the ice shelf.
This takes me to the question about the (average) thickness of the Ross Ice Shelf at its sea front, and whether this thickness (which is obviously stable) has been taken into account when it comes to possible MICI instabilities that demand a keel board of > 90-100 m discussed in other topics of this forum?

Andreas T

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Re: The Ross Ice Shelf Thread
« Reply #8 on: February 21, 2019, 10:49:57 PM »
Marine Ice Cliff Instability is a process which could affect grounded ice as far as I know. This would mean that a floating ice shelf (like Ross) may be affected by Marine Ice Shelf Instability but not MICI if its edge retreats to thicker parts of the shelf, which at the present is not happening.
I also think it is not the keel (below water) but the height above water (freeboard) which is critical. Iceshelves with a ice thickness of more than 300m are calving as tabular icebergs in Antarctica and in Greenland.

Stephan

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Re: The Ross Ice Shelf Thread
« Reply #9 on: February 22, 2019, 04:37:12 PM »
Thank you for that information.
I meant freeboard and not keel, sorry for having it mixed up.